<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script>
    function loadXMLDoc(){
        var xmlhttp;
        if (window.XMLHttpRequest)
        {
            //IE7+,Firefox,Chrome,Opera,Safari 浏览器执行代码
            xmlhttp=new XMLHttpRequest();
        }
        else 
        {
            //IE6,IE5浏览器执行代码
            xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
        }
        xmlhttp.onreadystatechange=function(){
            if (xmlhttp.readyState==4 && xmlhttp.status==200)
            {
                document.getElementById("myDiv").innerHTML=xmlhttp.responseText;
            }
        }
        xmlhttp.open("GET","https://www.runoob.com/try/ajax/ajax-info.txt",true);
        xmlhttp.send();
    }
    </script>
    </head>
    <body>
        <div id="myDiv">
            <h2>使用ajax修改该文本内容</h2>
        </div>
        <button type="button" onclick="loadXMLDoc()">修改文本内容</button>
    </body>
    </html>